It has been proposed that general abnormalities in structural and functional neuronal connectivity may underlie many of the triad of deficits observed in autism. A limited number of deficits at the neuronal level, widely expressed in multiple neurobehavioral systems could provide substantial explanatory power in autism. For example, abnormal temporal binding and weak central coherence may be related to alterations in brain functional and/or structural connectivity. Gamma band oscillatory activity, as measured using EEG and magnetoencephalography (MEG), has been associated with intrinsic GABAergic activity in animal and computational models of the neocortex and is thought to play an important role in binding and central coherence. We and others have published data demonstrating that gamma activity is abnormal in people with autism, possibly reflecting a cortical GABA dysfunction. Using a whole-head MEG system, we will assess patterns of auditory cortical synchronization with high precision in both time and frequency. As we are primarily interested in the development of new endophenotypes for autism, we will study parents of affected individuals as well as probands. Preliminary evidence from our laboratory indicates that a gamma- synchronization deficit may be familial. Forty families who have children with autism will be enrolled and the parents of the children will be assessed using MEG measures of gamma-band activity in auditory experiments. Their data will be compared to matched adults with no personal or family history of autism spectrum disorders their children. MEG measures of gamma power and phase-locking will be measured and associated with their structural underpinnings from magnetic resonance imaging (MRI) data and also with measures of the broad autism phrenotype.